Or, just do this:
Open Terminal
Type in: /usr/local/bin/svn ls https://......
It will ask you if you want to temporarily or permanently accept the "fishy" SSL. Type 'p' for permanent. Then go back to the checkout process from the SCplugin menu and complete your data transfer as outlined previously in this thread. Hope this helps. Sorry it's a month down the line.

1) Open Finder
2) Go to Go on the Bar at the top
3) Select connect to Server
4) Paste the URL for the SVN forever files
5) Select Guest
6) The file uploads to your computer
7) In the video it uploads to a neat file that's compressible, but on my computer it uploaded to a shared file that I couldn't compress here's what i did:
8) I selected all the files in the shared folder, copied and pasted them to a new folder i made on my desktop
9) then I compressed and uploaded the zip file to wordpress
and wallah it just uploaded perfectly. I was shocked to see that it was installed properly.